package io.nio;

/*
 * @(#)NBTimeServer.java 1.4 01/12/13 A non blocking Internet time server implemented using the New I/O (NIO) facilities
 * added to J2SE v 1.4. Copyright 2001-2002 Oracle and/or its affiliates. All rights reserved. Redistribution and use in
 * source and binary forms, with or without modification, are permitted provided that the following conditions are met:
 * -Redistributions of source code must retain the above copyright notice, this list of conditions and the following
 * disclaimer. -Redistribution in binary form must reproduct the above copyright notice, this list of conditions and the
 * following disclaimer in the documentation and/or other materials provided with the distribution. Neither the name of
 * Oracle and/or its affiliates. or the names of contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission. This software is provided "AS IS," without a warranty of any
 * kind. ALL EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING ANY IMPLIED WARRANTY OF
 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN AND ITS LICENSORS
 * SHALL NOT BE LIABLE FOR ANY DAMAGES OR LIABILITIES SUFFERED BY LICENSEE AS A RESULT OF OR RELATING TO USE,
 * MODIFICATION OR DISTRIBUTION OF THE SOFTWARE OR ITS DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR
 * ANY LOST REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL, INCIDENTAL OR PUNITIVE DAMAGES,
 * HOWEVER CAUSED AND REGARDLESS OF THE THEORY OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE SOFTWARE,
 * EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. You acknowledge that Software is not designed,
 * licensed or intended for use in the design, construction, operation or maintenance of any nuclear facility.
 */

import java.io.PrintWriter;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.spi.SelectorProvider;
import java.util.Date;
import java.util.Iterator;
import java.util.Set;

// Listen on a port for connections and write back the current time.
public class NBTimeServer {

    private static final int DEFAULT_TIME_PORT = 8900;

    // Constructor with no arguments creates a time server on default port.
    public NBTimeServer() throws Exception{
        acceptConnections(this.DEFAULT_TIME_PORT);
    }

    // Constructor with port argument creates a time server on specified port.
    public NBTimeServer(int port) throws Exception{
        acceptConnections(port);
    }

    // Accept connections for current time. Lazy Exception thrown.
    private static void acceptConnections(int port) throws Exception {
        // Selector for incoming time requests
        Selector acceptSelector = SelectorProvider.provider().openSelector();

        // Create a new server socket and set to non blocking mode
        ServerSocketChannel ssc = ServerSocketChannel.open();
        ssc.configureBlocking(false);

        // Bind the server socket to the local host and port

        InetAddress lh = InetAddress.getLocalHost();
        InetSocketAddress isa = new InetSocketAddress(lh, port);
        ssc.socket().bind(isa);

        // Register accepts on the server socket with the selector. This
        // step tells the selector that the socket wants to be put on the
        // ready list when accept operations occur, so allowing multiplexed
        // non-blocking I/O to take place.
        SelectionKey acceptKey = ssc.register(acceptSelector, SelectionKey.OP_ACCEPT);

        int keysAdded = 0;

        // Here's where everything happens. The select method will
        // return when any operations registered above have occurred, the
        // thread has been interrupted, etc.
        while ((keysAdded = acceptSelector.select()) > 0) {
            // Someone is ready for I/O, get the ready keys
            Set readyKeys = acceptSelector.selectedKeys();
            Iterator i = readyKeys.iterator();

            // Walk through the ready keys collection and process date requests.
            while (i.hasNext()) {
                SelectionKey sk = (SelectionKey) i.next();
                i.remove();
                // The key indexes into the selector so you
                // can retrieve the socket that's ready for I/O
                ServerSocketChannel nextReady = (ServerSocketChannel) sk.channel();
                // Accept the date request and send back the date string
                Socket s = nextReady.accept().socket();
                // Write the current time to the socket
                PrintWriter out = new PrintWriter(s.getOutputStream(), true);
                Date now = new Date();
                out.println(now);
                out.close();
            }
        }
    }

    // Entry point.
    public static void main(String[] args) {
        // Parse command line arguments and
        // create a new time server (no arguments yet)
        try {
            NBTimeServer nbt = new NBTimeServer();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}
